Turbochargers having a configuration in which a rotating shaft is supported by a rolling bearing have been known from the related art. To describe specifically, a turbocharger includes a housing having a tubular space for housing the rolling bearing. By fitting an outer ring of the rolling bearing into the space of the housing, the rolling bearing is installed in the housing. The rotating shaft of the turbocharger is inserted through a rotatable inner ring. The rotating shaft is made rotatable relative to the housing.
This type of turbocharger includes a structure for supplying oil that is lubricant to the rolling bearing. To describe specifically, in the turbocharger in which the rotating shaft extends in a horizontal direction, an oil supply flow passage that communicates with the space of the above-described housing is formed in an upper portion (a portion up to an upper half or so in a sectional view) of the housing. An oil supply port that communicates with the oil supply flow passage is formed in an upper portion of the outer ring of the rolling bearing. The oil supplied to the oil supply flow passage flows into the inside of the outer ring through the oil supply port, flows along an inner peripheral surface of the outer ring or an outer peripheral surface of the inner ring, and is supplied to between rolling elements (balls) of the rolling bearing, and raceways. A minute clearance is between an inner peripheral surface of the space of the above-described housing and an outer peripheral surface of the outer ring of the rolling bearing. The oil enters this clearance from the oil supply flow passage. The oil flows around an outer periphery of the outer ring, and consequently, an oil film is interposed between the inner peripheral surface of the space of the housing and the outer peripheral surface of the outer ring. Accordingly, the turbocharger can obtain a damping effect (an effect of damping vibration) caused by a squeeze film damper phenomenon of this oil film at the time of generation of vibration. Both ends of the outer ring in an axial direction are open, respectively. These opening ends communicate with an oil discharge flow passage formed in a lower portion of the housing. The oil supplied to between the rolling elements of the rolling bearing and the raceways flows out to the oil discharge flow passage through the opening ends on both sides of the outer ring.
Meanwhile, the following PTL 1 discloses a turbocharger including a rolling bearing in which an oil reservoir recess is formed in the outer peripheral surface of the outer ring (bearing housing) in order to reserve lubricating oil (lubricant) at the outer periphery of the outer ring (bearing housing).